BACKGROUND OF THE INVENTION 1. Field Of The Invention The present invention relates to a subsurface safety valve used for controlling fluid flow in a well conduit and, more particularly, to an equalizing subsurface safety valve.

2. Description Of The Related Art Subsurface safety valves are commonly used in wells to prevent uncontrolled fluid flow through the well in the event of an emergency, such as to prevent a well blowout.

Conventional safety valves use a flapper which is biased by a spring to a normally closed position, but is retained in an open position by the application of hydraulic fluid from the earth's surface. A typical subsurface safety valve is shown and described in U.S. Pat. No.

4,161,219, which is commonly assigned hereto.

When the flapper is in the closed position, well fluid pressure below the flapper acting upon a relatively large surface area of the flapper makes opening of the flapper difficult. This difficulty in opening cannot be easily overcome simply by increasing the force exerted against the flapper by an opening piston and cylinder assembly because the relatively small cross- sectional area of the opening piston and cylinder assembly would require a fluid pressure that may burst the control line carrying hydraulic fluid from the earth's surface to the piston and cylinder assembly. Additionally, when the flapper is opened the initial flow of well fluid is relatively rapid which tends to etch, or erode, the primary sealing surface of the flapper. Any

damage to this primary sealing surface is extremely critical because it is this sealing surface which must be intact to prevent uncontrolled flow of well fluids and to prevent a possible well blow out. The present invention solves these difficulties by providing a subsurface safety valve with an equalizing mechanism to allow the pressure above and below the flapper to equalize prior to the complete opening of the flapper.

SUMMARY OF THE INVENTION The present invention is directed generally to a subsurface safety valve with a pressure equalizing mechanism. In a broad aspect, the equalizing subsurface safety valve of the present invention includes a body member having a longitudinal bore extending therethrough; a valve actuator disposed for axial movement within the longitudinal bore; means for controllably moving the valve actuator within the longitudinal bore; a valve member mounted within the body member to control fluid flow through the longitudinal bore, the valve member having an upper surface, a lower surface, and a bore therethrough; means for biasing the valve member to a normally closed position to prevent fluid flow through the longitudinal bore; means for biasing the valve actuator away from the valve member; an equalizing plug disposed for reciprocal movement within the bore of the valve member for controlling fluid flow through the valve member; a strike plate having a periphery and an actuating member, the strike plate extending into a path of the valve actuator, the actuating member extending downwardly from the strike plate into the bore through the valve member and being connected to the equalizing plug; and a spring disposed between the strike plate and the upper surface of the valve member adjacent the periphery of the strike plate for upwardly biasing the strike plate away from the valve member and for upwardly biasing the equalizing plug within the bore through the valve member, whereby downward movement of the valve actuator is transferred through the strike plate to the equalizing plug to shift the plug

to open a passageway through the valve member and permit fluid pressure above and below the valve member to equalize before the valve member is opened to allow fluid flow through the longitudinal bore of the body.

Another feature of the present invention is that the means for controllably moving the valve actuator within the longitudinal bore includes a piston and cylinder assembly mounted to the body member with one side of the assembly adapted to be in communication with a source of hydraulic fluid for moving the valve member to the open position to permit fluid flow through the longitudinal bore. Another feature of the present invention is that the valve member is a flapper valve. Another feature of the present invention is that the valve member is a curved flapper valve. Another feature of the present invention is that the equalizing plug is a generally cylindrical plug having an upper portion and an enlarged annular sealing surface adjacent a first end thereof for cooperable sealing engagement with a sealing surface formed within the bore of the valve member. Another feature of the present invention is that the enlarged annular sealing surface further includes a metallic annular sealing surface. Another feature of the present invention is that the sealing surface within the bore of the valve member further includes an annular sealing surface. Another feature of the present invention is that the annular sealing surface within the plug bore further includes a metallic portion and a pliable portion. Another feature of the present invention is that the equalizing plug is held in a normally closed position by action of the spring against the strike plate. Another feature of the present invention is that the upper portion of the equalizing plug is disposed below the upper surface of the valve member. Another feature of the present invention is that fluid pressure within the well conduit is equalized through an internal fluid flow passageway formed through the equalizing plug and strike plate.

Another feature of the present invention is that the equalizing plug further includes an upper portion having a generally longitudinal bore, a generally longitudinal passageway, and at least one generally radially disposed opening, the bore extending downwardly from an upper surface of the equalizing plug and having a threaded portion, the passageway extending downwardly from the bore and being disposed in fluid communication with the at least one radially disposed opening, the at least one radially disposed opening exiting the plug at a location between a lower surface of the bore and the sealing surface on the shoulder of the plug; and the actuating member further includes a shank having a threaded portion for mating with the threaded portion of the bore in the upper portion of the plug, and a generally longitudinal passageway extending upwardly from a lower surface on the shank through the actuating member to an upper surface of the strike plate and cooperating with the longitudinal passageway and the at least one radially disposed opening in the equalizing plug to establish an internal fluid flow passageway through the valve member to equalize the fluid pressure above and below the valve member. Another feature of the present invention is that the longitudinal passageway extending through the actuating member further includes a flared portion adjacent the upper surface of the strike plate. Another feature of the present invention is that the upper surface of the valve member further includes a radial lip for receiving the strike plate and forming a groove for receiving the spring. Another feature of the present invention is that the spring is a compression spring. Another feature of the present invention is that the compression spring is a wave spring. Another feature of the present invention is that the compression spring is a Belleville spring.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an elevational side view, partially in cross-section, showing a subsurface safety valve of the present invention.

Figure 2 is an elevational side view, in cross-section, showing an equalizing mechanism of the present invention installed in the flapper mechanism of the subsurface safety valve shown in Figure 1, with both the flapper mechanism and the equalizing mechanism in closed positions.

Figure 3 is a fragmentary elevational view similar to Figure 2, showing an equalizing mechanism of the present invention installed in the flapper mechanism of the subsurface safety valve shown in Figure 1, with both the flapper mechanism and the equalizing mechanism in closed positions.

Figure 4 is an exploded elevational view showing the relationship between an equalizing plug of the present invention and a strike plate of the present invention.

Figure 5 is a view similar to Figure 3, with the flapper mechanism still in a closed position, except that a flow tube has now moved downwardly to displace the equalizing mechanism of the present invention into an equalizing position.

Figure 6 is a fragmentary elevational view showing the flapper mechanism of the present invention in an open position and the equalizing mechanism of the present invention in its closed position.

DETAILED DESCRIPTION OF THE INVENTION For purposes of the following description, it will be assumed that the present invention is installed within a subsurface safety valve of the type shown in U.S. Pat. No.

4,161,219, which type is commonly referred to as a rod-piston safety valve. However, it should be understood that the present invention can be used in any commercially available safety valve, whether it be tubing conveyed, wireline conveyed, hydraulically operated, or electrically operated.

Referring to the drawings in detail, wherein like numerals denote identical elements throughout the several views, there is shown in Figure 1 a specific embodiment of a subsurface safety valve 10 constructed in accordance with the present invention. With reference to Figure 1, the subsurface safety valve 10 of this specific embodiment is comprised of a generally tubular body 12 with a longitudinal bore 14 that extends therethrough. Each end of the body 12 includes mechanisms, such as threads 16, for interconnection with a pipe string (not shown) suspended within a wellbore (not shown). A sleeve member 18, usually referred to as a flow tube, is disposed within the bore 14 and is adapted for axial movement therein. The flow tube 18 includes a spring 20 disposed therearound that acts upon a shoulder 22 on the flow tube 18 biasing the flow tube 18 away from a flapper mechanism 24. The present invention is not intended to be limited to any particular means for biasing the flow tube 18 away from the flapper 24. For example, instead of, or in addition to, the spring 20, the valve 10 may utilize a balancing gas chamber (not shown), such as those disclosed in U.S. Patent Nos. 4,252,197 (Pringle), 4,660,646 (Blizzard), 4,976,317 (Leismer), and 5,310,004 (Leismer), all of which are commonly assigned hereto and incorporated herein by reference.

Referring to Figures 2 and 3, the flapper mechanism 24 generally comprises a disc or flapper valve closure member 26 with an arm 28 on a peripheral edge thereof that is hingedly connected to an annular housing 30 mounted within the bore 14. In a specific embodiment, the annular housing 30 includes a metallic annular sealing surface 32 cooperable with an annular sealing surface 34 on the flapper 26. In a specific embodiment, the annular housing 30 may further include a secondary annular sealing surface 38 formed from an annular body of pliable material, which is cooperable with the annular sealing surface 34 on the flapper 26.

The metallic sealing surface 32 is generally referred to as the "hard seat" and the pliable sealing surface 38 is generally referred to as the "soft seat".

As shown in Figure 1, in a specific embodiment, a rod-piston system may be provided to open the flapper 26, and may be comprised of a piston 40 sealably mounted for reciprocal movement within a cylinder 42 located within the wall of the tubular body 12. A first end 41 of the piston 40 is in contact with hydraulic fluid (not shown) provided thereto from the earth' s surface through a relatively small diameter control conduit 44. A second end 43 of the piston 40 is operatively connected, in any suitable manner, to the flow tube 18. When the pressure of hydraulic fluid in the control conduit 44 exceeds the force needed to compress the spring 20, the piston 40 is forced downwardly, thereby causing the flow tube 18 to come into contact with, and open, the flapper 26. In the event that the hydraulic pressure applied to the piston 40 is decreased, as by command from the earth's surface or by the control conduit 44 being damaged, the spring 20 forces the flow tube 18 upwardly away from the flapper 26.

The flapper 26 is then rotated, and biased, into a closed position by action of a hinge spring (not shown) to permit the annular sealing surfaces 32, 34 and 38 to mate and thereby establish a fluid seal to prevent fluid flow into the flow tube 18.

As has been described above, when the flapper 26 has been closed, the pressure of fluids within the bore 14 upstream of (i.e., below) the closed flapper 26 increases and the pressure of the wellbore fluids downstream of (i.e., above) the closed flapper 26 decreases as the wellbore fluids remaining above the flapper 26 are recovered to the earth's surface through the pipe string. This creates a large pressure differential across the flapper 26 such that reopening of the flapper 26 becomes difficult. This difficulty in opening the flapper 26 cannot be easily overcome simply by increasing the force exerted against the lower surface of

the flapper 26, because the relatively small cross-sectional area of the opening piston 40 and cylinder 42 would require a fluid pressure that may burst the control conduit 44 carrying the hydraulic fluid. The present invention solves this difficulty in opening the flapper 26 by providing the flapper mechanism 24 with pressure equalizing mechanism, described below, to allow the pressure above and below the flapper 26 to equalize prior to the complete opening of the flapper 26, thereby reducing the force necessary to open the flapper 26.

The equalizing mechanism of the present invention is best shown in Figures 3-5.

Referring to Figure 3, in a specific embodiment of the present invention, the flapper mechanism 24 is provided with an equalizing mechanism which includes: an equalizing plug 46; a bore 48 through the flapper 26 for receiving the plug 46; a circular strike plate 50 having an actuating member 52 extending downwardly from the strike plate into the plug bore and connected to the equalizing plug 46, the strike plate extending into the path of the flow tube 18 and transferring downward movement of the flow tube 18 to the plug 46 to thereby shift the plug 46 axially downwardly to open a passageway through the flapper 26 and permit the fluid pressure above and below the flapper 26 to equalize; and a spring 54 disposed between the strike plate 50 and the upper surface of the flapper 26 and adjacent the periphery 56 of the strike plate 50 for upwardly biasing (a) the strike plate 50 away from the flapper 26 and (b) the equalizing plug 46 within the bore 48. In a specific embodiment, the upper surface 27 of the flapper 26 may be provided with a radial lip 84 for receiving the strike plate 50 and forming a groove 86 for receiving the spring 54. The spring 54 may be any suitable compression spring as known to those having ordinary skill in the art, such as a wave spring or a Belleville spring.

The plug 46 is disposed for reciprocal movement within the plug bore 48. The plug 46 is held in a normally closed position by action of the spring 54 against the strike plate 50.

The plug 46 includes an enlarged shoulder 58 on a first end thereof and an upper portion 60 on an opposite second end thereof. The upper portion 60 of the plug 46 is disposed below the upper surface 27 of the flapper 26. The enlarged shoulder 58 includes a metallic annular sealing surface 62 that cooperates with a metallic annular sealing surface 64 (or "hard seat") on the flapper 26 about the plug bore 48. In a specific embodiment, the bore 48 of the flapper 26 may also include a secondary annular sealing surface (or "soft seat") (not shown) formed from an annular body of pliable material to cooperate with a mating secondary annular sealing surface (not shown) on the enlarged shoulder 58 of the plug 46. Preferably, a soft seat is used to ensure sealing when operating in low pressure differential applications.

As best shown in Figure 4, the upper portion 60 of the plug 46 includes a generally longitudinal bore 66 extending from the upper surface 68 of the plug 46 and having a threaded portion 70. The upper portion 60 of the plug 46 further includes a generally longitudinal passageway 72 which extends from the bore 66 and is in fluid communication with one or more generally radially disposed openings 74 that exit the plug 46 at a location between the lower surface of the bore 66 and the sealing surface 62 on the shoulder 58 of the plug 46. The purpose of the bore 66, the passageway 72, and the openings 74 will be described below.

Still referring to Figure 4, the actuating member 52, which extends downwardly from the strike plate 50, includes a shank 76 having a threaded portion 78 for mating with the threaded portion 70 of the bore 66 in the upper portion 60 of the plug 46. A generally longitudinal passageway 80 extends from the lower surface 77 of the shank 76 through the

actuating member 52 to the upper surface 51 of the strike plate 50. The passageway 80 cooperates with the longitudinal passageway 72 and the one or more radially disposed openings 74 in the plug 46 to establish an internal fluid flow passageway through the flapper 26 to equalize the fluid pressure above and below the flapper 26, as more fully explained elsewhere herein. In a specific embodiment, the longitudinal passageway 80 may be provided with a flared portion 82 adjacent the upper surface 51 of the strike plate 50 to enhance the fluid flow rate through the flapper 26.

When the flapper 26 is in a closed position, as shown in Figures 1-3, and it is desired to open the flapper 26, the flow tube 18 is forced towards the flapper 26 by the application of hydraulic fluid through the control conduit 44 (as has been described previously) or by electrical/mechanical action or simply mechanical action, depending upon the type of safety valve within which the present invention is included. With reference to Figure 3, as the flow tube 18 is moved downwardly, a lower portion of the flow tube 18 will come into contact with the upper peripheral surface 56 of the strike plate 50. The lower portion of the flow tube 18 is formed from material sufficiently hard to not be deformed, or galled, by contact with the strike plate 50, or the lower portion of the flow tube 18 can include a surface hard coating or can be formed as a separate piece joined thereto and formed from harder material than the other portions of the flow tube 18. As the strike plate 50 is pushed downwardly, it will shift the plug 46 axially downwardly so as to separate the annular sealing surfaces 62 and 64 and expose the one or more radially disposed openings 74. The relatively high pressure wellbore fluid below the flapper 26 then rapidly flows into the one or more radially disposed openings 74, through the longitudinal passageway 72 in the plug 46, through the longitudinal passageway 80 in the strike plate 50, and into the bore 14 above the flapper 26. Since the

radially disposed openings 74 are displaced from the annular sealing surfaces 62 and 64, the relatively rapid flow of wellbore fluids will not damage the sealing surfaces 62 and 64. In this manner, an internal fluid flow passageway is opened through the flapper 26, thereby permitting the fluid pressure above and below the flapper 26 to equalize.

In operation, the flow tube 18 travels axially downward, activating the equalizing mechanism and coming to rest against the flapper 26 until pressure equalization has occurred, and then proceeds with the opening of the flapper 26. In this manner, the pressure differential across the flapper 26 is equalized through the plug 46 prior to the opening of the flapper 26.

As such, the equalizing mechanism of the present invention prevents the initial relatively high velocity flow of fluids past the flapper 26 from damaging the annular sealing surfaces 32, 34, and 38. To complete the opening of the flapper 26, the flow tube 18 is forced against the flapper 26 with sufficient force to overcome the force exerted by the hinge spring (not shown), the force exerted by the spring 20, and the force exerted by the pressure in the tubing, and hold the flapper 26 in the open position, as shown in Figure 6, as long as the hydraulic pressure from the control conduit 44 is applied. When the flapper 26 is in the open position, the plug 46 is maintained by action of the spring 54 in its closed or sealed position. In this manner, excessive exposure of the sealing surfaces 62 and 64 to production fluids is prevented. When the hydraulic pressure from the control conduit 44 is reduced or removed, the spring 20 causes the flow tube 18 to be moved away from the flapper 26, so that: (a) the flapper 26 rotates to a closed position and the sealing surfaces 32, 34 and 38 come into operative contact with each other to prevent fluid flow therepast; and (b) the flow tube 18 moves away from the strike plate 50 so that the plug 46 is upwardly biased into the plug bore 48 by the spring 54, the radially disposed openings 74 are closed, and the sealing surfaces 62

and 64 come into operative contact with each other to prevent fluid flow therepast. During the closing of the flapper 26, the equalizing plug 46 may be opened for a very brief time, but will return to the closed position as soon as there ceases to be contact between the strike plate 50 and the flow tube 18.

In another specific embodiment, the equalizing mechanism of the present invention may be installed within a curved flapper valve of the type disclosed in U.S. Pat. No.

4,926,945, commonly assigned hereto, which is incorporated herein by reference.

It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials or embodiments shown and described, as obvious modifications and equivalents will be apparent to one skilled in the art.